1. Field of the Invention
This invention relates to a circuit for detecting the flow of an excess of reverse power from a load to a power supply, such as an uninterruptible power system, to cause disconnection of the power supply from the load.
2. Description of the Prior Art
In reverse power detection systems of the type described in U.S. Pat. No. 3,539,868, reverse current is detected, by monitoring the phase of a corresponding voltage signal. Under these circumstances, it is assumed that reverse power is flowing, and if the current is above a designated threshold level, a detection signal will be generated. However, the actual magnitude of reverse power is never really detected. It is conceivable that when reverse current above a threshold value is detected, the magnitude of the corresponding voltage signal could be very small. Thus, while an acceptable small amount of reverse power may actually be flowing, if the detected reverse current is greater than a specified magnitude, a system will still be shut down. Inasmuch as this and other systems described in the prior art only provide a guess of the flow of reverse power, rather than providing an actual determination of the real magnitude of reverse power, there is no accurate way of determining when to disconnect a power system from its load if an excess of reverse power is actually flowing back from a load into a power system.